> That leaves innate desire, which just doesn't seem to be that strong. We don't need to posit some recent drop in innate desire to explain the drop in fertility rates. The historical behavior we see fits just fine with innate desire being constant, and just not that high.
It varies from person to person; some of that variation is social/cultural influences, some is life experiences/circumstances, some is just randomness-but very likely it has a genetic component.
If certain alleles predispose one to be more likely to desire to have children, then in a society with strong social pressure to have children and limited availability of contraception, the selective pressure in favour of those alleles is going to be limited; in a society where social pressure to have children is low and contraception is readily available, those alleles will significantly increase the odds of having children, likely resulting in their frequency increasing over time, and maybe even (in the very long-run) a rebound in TFR
It varies from person to person; some of that variation is social/cultural influences, some is life experiences/circumstances, some is just randomness-but very likely it has a genetic component.
If certain alleles predispose one to be more likely to desire to have children, then in a society with strong social pressure to have children and limited availability of contraception, the selective pressure in favour of those alleles is going to be limited; in a society where social pressure to have children is low and contraception is readily available, those alleles will significantly increase the odds of having children, likely resulting in their frequency increasing over time, and maybe even (in the very long-run) a rebound in TFR